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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 852 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

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  1. 1.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  2. 2.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 24° and angle B = 91°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  5. 5.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  8. 8.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  9. 9.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  10. 10.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  14. 14.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  15. 15.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  21. 21.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 24° and 31°. What is the exterior angle (in degrees)?
  25. 25.Can a triangle have sides of 6 cm, 4 cm and 8 cm? (a) Yes (b) No
  26. 26.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  27. 27.Can a triangle have sides of 22 cm, 10 cm and 8 cm? (a) Yes (b) No
  28. 28.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 27° and 39°. What is the exterior angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 43° and 23°. What is the exterior angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 34° and 55°. What is the exterior angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 63° and 54°. What is the exterior angle (in degrees)?
  33. 33.In triangle ABC, angle A = 56° and angle B = 90°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 59° and angle B = 57°. What is angle C (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  36. 36.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 35° and angle B = 38°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 6 cm, 13 cm and 7 cm? (a) Yes (b) No
  40. 40.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?

Answer key

  1. 15
  2. 70
  3. 65
  4. 35
  5. 72
  6. 45
  7. 20
  8. 30
  9. 9
  10. 64
  11. 26
  12. 11
  13. 30
  14. 17
  15. 76
  16. 128
  17. 62
  18. 47
  19. 65
  20. 25
  21. 15
  22. 74
  23. 47
  24. 55
  25. Yes
  26. 59
  27. No
  28. 41
  29. 66
  30. 66
  31. 89
  32. 117
  33. 34
  34. 64
  35. 30
  36. 48
  37. 40
  38. 107
  39. No
  40. 7

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